1. Field of the Invention
The invention relates to a method for determining the nature and amount of salt water held in used oils, especially marine oils. In particular, the method is designed for use on board ship to avoid any delay that is caused when necessary to reach a land-based laboratory for the determination.
2. Discussion of the Prior Art
Various methods have been used to detect the presence of sea water in lubricating oil, particularly marine oils. Generally, such methods are based on the determination of chloride in a sample of the oil. In testing for chlorides by an early method, samples of the used marine lubricating oil were diluted with a suitable light solvent, centrifuged, and the separated water phase at the bottom of the centrifuge tube was removed for chloride analysis. The analysis was carried out by adding silver nitrate to the separated water phase. The formation of insoluble silver chloride in the form of a white precipitate denoted a positive test for the presence of the chloride ion. This test was found to be far from satisfactory in laboratory use, and it was practically unworkable in the field, for example, in marine ports or emergency ports, where laboratory facilities are not available. If, after centrifuging of the lubricating oil, a water phase is not formed, no test can be made for chloride ion, although the oil may actually have chloride contamination. In addition, such tests require, by necessity, a centrifuge and various assorted glassware apparatus, a delicate manipulation to remove water from the centrifuge tube, personal safety considerations in handling of strong acids, relatively easy contamination of chemicals in a marine atmosphere, and the possibility of inaccurate conclusions by reason of the precipitation of organic acids in a manner similar to that of the chlorides.
An improvement to the above-described method is taught in U.S. Pat. No. 3,202,483. In carrying out the chloride determination as described in the patent, a hydrocarbon, water and an emulsion breaker are used to extract the chloride. The chloride containing aqueous solution is then brought into contact with a composite of silver chromate deposited on an absorbent, e.g. silica gel contained in a glass tube. However, the emulsion-breaking action was erratic. Also, the water extract lay below the oil phase so that when the tube containing the silver chromate and absorbent was pushed through the oil phase, the tube picked up oil. Both these difficulties often led to erroneously low chloride values. The present invention relates to an improved system for extracting the chloride.